The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
An RF filter that is a core component of a mobile communication system is manually manufactured by a skilled worker using a tuning screw in order to make up structural characteristics (process and assembly tolerances and the like).
However, such a manual process needs considerable proficiency and exhibits markedly different outputs depending on personal capability and the available manpower. Accordingly, rising labor costs lead to loss of cost competitiveness.
Besides, one of the severe problems in the manual production process lies in the fact that all the products are different from one another in their quality. Numerous companies and engineers have conducted research and development to automate the labor intensive manufacturing process, and accordingly a few products have been disclosed. However, their inherent tuning screw arrangement hindered evolution into successful automation in the RF filter production.
In order to fundamentally solve such deficiency, a bellow filter has been developed and commercialized without using a turning screw to adjust a resonance frequency, along with an automatic tuning apparatus developed for tuning the bellow filter.
However, the existing automatic tuning apparatus was manufactured in such a way that the tuning apparatus measures phase values of respective resonance elements at an input port or output port of the filter and then tunes the respective resonance elements sequentially (when tuning resonance element 1, resonance element 2 and all the rest are electrically shorted), which is followed by removal of shorting pins before the subsequent tuning session.
Here, the existing automatic tuning apparatus requires screws, which adjusts a coupling (resonance separation distance) between the resonance elements, to be manually assembled in advance to predetermined lengths, and requires a skilled worker to perform a secondary tuning if the overall characteristics of the filter fail to meet a target value even after the automatic tuning.